problem rendering moving objects

[rohitarora]

hi guys!!! its been like past two days that i am stuck with this strange problem,i was trying to render a scene where i have a moving camera and a moving character,i have rendered both the back drop scene and the moving human using the matte object method,but when i save the png output and merge them in ps i get this blank area halo around the human,it would gr8 if any one could save me out of this issue.

[Corey Beaulieu]

It looks like you set your characters alpha to -1 along with everything else. Could be wrong, but it's my first instinct.

[rohitarora]

i did use -1 alpha, but that is when i didn't wanted the character to be visible in my scene,and inverted the process when i just wanted the human to render as a separate pass.

every thing renders perfectly but when i merge both the layers it seems as if some pixels have gone missing..

 

may be i am following a wrong process,if possible can you share what method i should follow to render the scene with camera movement and the humans moving around,i cant use animation pre-pass method as my scene is huge .thanx in advance

Edited January 26, 2012 by rohitarora

[Corey Beaulieu]

If you need to render them separately then just render the scene with the character off and when you render the character:

 

Select everything in your scene except for the character and go to Vray Properties (I'm making the assumption you are using Vray)

check the "Matte Object" box and change alpha to -1. Also check "Shadows" and "Affect Alpha"

 

Don't change your characters alpha, leave it at 1.

 

Render.

 

The only other thought is that if you are compositing an animation in Photoshop, the interpret video function doesn't work (at least not for me) and you cannot utilize your alpha channel. You are better off trying after effects for this composite.

 

 

Also: why are you rendering it separately? At least so far it doesn't seem like the type of scene that is going to get hugely color corrected and beefed-up in post. If it's a simple animation just render them together.

[rohitarora]

Hey thanx a ton buddy for your time and efforts,really appreciate it,

actually this is not my final scene this is just a test scene i did to check the final output i will get,

 

problem is my humans are walking behind a glass door and railing in the scene,so if i just simply hide humans and render the scene first and then render the humans in a separate pass i can't superimpose the image of humans over the glass railing and doors,as the are actually behind it.

 

yes i am using vray and following the same method and even tried to composite it in AE,but got the same problem.

 

if you can just try a small test :

create a plane and a tea pot over it,now make the tea pot a matte object and render the scene,save the output in png,

 

now invert selection and make the plane matte object, now the tea pot will render and plane wont render,

 

now save both the renders in png format,and try to composite it in AE you will understand the issue.

 

please find the zip file and test your own render,pixel around the teapot are missing..hope this makes the problem more understandable. thanx

[Corey Beaulieu]

Well I think I understand a little better. By halo you simply mean that you can see the out line of the character? The pictures you showed in your post made it look like you were saying your character was an alpha.

 

2 things:

 

Either interpret the top layer as premultiplied black and leave the bottom layer as straight (teapot premultiplied, plane straight)

 

and/or

 

render them as EXRs, half float. This has the cleanest alpha channel. No Halo's.

[Tommy L]

You may also have some filtering applied to the bitmap. Open in material editor and change filtering to none.